1. Field of the Disclosure
This disclosure relates generally to a system and methods for managing the supply of additives or chemicals into wellbores and wellsite hydrocarbon transporting and processing units.
2. Background of the Art
A variety of chemicals (also referred to herein as “additives”) are often introduced into producing wells and wellsite hydrocarbon treatment and processing units so as to control formation of, among other things, corrosion, scale, paraffin, emulsion, hydrate, hydrogen sulfide, asphaltene and other harmful chemicals. In production wells, additives are usually injected through one or more tubes (also referred to herein as lines) that are run from the surface to one or more locations in the wellbore. Additives are introduced proximate electrical submersible pumps (as shown for example in U.S. Pat. No. 4,582,131, which is assigned to the assignee hereof and incorporated herein by reference). The additives may be introduced through an auxiliary tube associated with a power cable used with the electrical submersible pump (“ESP”) (such as shown in U.S. Pat. No. 5,528,824, assigned to the assignee hereof and incorporated herein by reference). Additives also are introduced into adjacent production zones to inhibit the formation of the harmful chemicals. Additionally, additives often introduced into the wellsite fluid treatment and processing apparatus and pipeline transporting the treated hydrocarbons from the wellsite.
For oil well applications, a high pressure pump is typically used to inject one or more additives into the well from a source thereof at the wellsite, such as a chemical tank. The pump is usually set to operate continuously at a designated speed (frequency) or at a specified stroke length to control the amount of the injected additive. A separate pump and an injector are typically used for each type of additive. Manifolds are sometimes used to inject additives into multiple wells from a common additive source. A substantial number of wells are unmanned. A large number of such wells are located in unmanned remote areas or offshore platforms. Additive injection systems used at such wells are often not serviced routinely, which can result in the malfunction of such a system, thereby either injecting incorrect amounts of additives or in some cases becoming totally inoperative. Injecting excessive amounts of additives can increase the operating cost of the well, while inadequate amounts of the additives can cause the formation of scale, corrosion, hydrate, emulsion, asphaltene.
The operating condition of a well, the effectiveness of the equipment in the well, as well as those of the production zones (reservoirs) often change over time, requiring altering the amount and type of the additives for preserving the health of downhole equipment and for the efficient production of hydrocarbons at optimal costs. The changes in the well conditions may occur due to: changes in the fluid flow rates from one or more production zones; changes in the composition of the produced fluids, such as the amount of water in the fluid; formation of chemicals downhole, such as scale, corrosion, paraffin, hydrate, emulsions, asphaltene, etc.; depletion of the additives in the surface tank or leaks in the additive tanks or tubes; failure of one or more downhole devices, such as a valve, choke, and ESP; degradation of casing and cement bond between the casing and the formation; water breakthrough or the occurrence of a cross flow condition, etc. Inadequate or incorrect supply of additives can cause the build-up of chemicals such as cale, hydrate, paraffin, emulsion, corrosion, asphaltene, etc., which can: clog and corrode downhole equipment; reduce hydrocarbon production from the well; reduce the operating life of the well equipment; reduce the operating life of the well itself; require expensive rework operations; or cause the abandonment of the well. Excessive corrosion in a pipeline, especially in a subsea pipeline, can reduce the flow through the pipeline or rupture the pipeline and contaminate the surrounding environment. Repairing subsea pipelines can be cost-prohibitive.
Commercially-used well site additive injection systems usually require periodic manual inspection to determine whether the additives are being dispensed correctly. Such systems typically do not supply relatively precise amounts of additives or continuously monitor the actual amount of the additives being dispensed, determine the impact of the dispersed additives, vary the amount of dispersed additives as needed to maintain certain parameters of interest within their respective desired ranges, communicate necessary information to onsite personnel (when present) and offsite locations and take actions in response to commands received from such onsite and offsite locations. Such systems also typically do not control additive injection into multiple wells in an oilfield or into multiple wells at a wellsite, such as an offshore production platform.
Additionally, the present chemical injection systems do not determine the overall impact of various chemicals being produced on the equipment in the well, flow rates from each production zone and the overall economic impact on the production from the well. Such systems also do not tend to optimize or maximize fluid production from different zones or the well as a whole, perform forward looking analysis or take actions corresponding to such forward looking analysis.
Therefore, there is a need for an improved chemical injection system.